% cprog.tex (or cprog.sty) - formatting of C programs
% By Eamonn McManus <emcmanus@cs.tcd.ie>.  This file is not copyrighted.
% $Header: cprog.tex,v 1.2 90/03/13 17:51:05 emcmanus Exp 
% $
% see further comments at the end of the file

% This allows C programs to be formatted directly by TeX.  It can be
% invoked by \cprogfile{filename} or (in LaTeX) \begin{cprog} ...
% \end{cprog} or (in plain TeX) \cprog ... \end{cprog}.  In LaTeX, the
% alternative form \begin{cprog*} is allowed, where spaces in C strings
% are printed using the `square u' character (like LaTeX {verbatim*}).
% In plain TeX, you have to use \csname cprog*\endcsname for this (sorry).
% If you are using \cprogfile, say \cprogttspacetrue beforehand if you
% want this effect.

% The formatting is (necessarily) simple.  C text is set in a normal Roman
% font, comments in a slanted font, and strings in a typewriter font, with
% spaces made visible as the `square u' symbol.  Tabs are expanded to four
% spaces (this does not look good when comments are aligned to the right of
% program text).  Some pairs of input characters appear as single output
% characters: << <= >> >= != -> are respectively TeX's \ll \le \gg \ge \ne
% \rightarrow.

% The fonts below can be changed to alter the setting of the various parts
% of the program.  The \cprogbaselineskip parameter can be altered to
% change the line spacing.  LaTeX's \baselinestretch is taken into account
% too.  The indentation applied to the whole program is \cprogindent,
% initially 0.  Before and after the program there are skips of
% \beforecprogskip and \aftercprogskip; the default values are \parskip
% and 0 respectively (since there will often be a \parskip after the
% program anyway).

% This package works by making a large number of characters active.  Since
% even spaces are active, it is possible to examine the next character in
% a macro by making it a parameter, rather than using \futurelet as one
% would normally do.  This is more convenient, but the coding does mean
% that if the next character itself wants to examine a character it may
% look at a token from the macro rather than the input text.  I think that
% all cases that occur in practice have been looked after.

% The macros were thrown together rather quickly, and could do with some
% work.  For example, the big macro defined with @[] taking the place of
% \{} could be recoded to use \{} and so be more legible.  The grouping of
% two-character pairs should be controllable, since not everyone will want
% it.  The internal macros etc should have @ in their names, and should be
% checked against LaTeX macros for clashes.

% Allow multiple inclusion to go faster.
\ifx\undefined\cprogsetup       % The whole file.

% Define the fonts used for program text, comments, and strings.
% Note that if \it is used for \ccommentfont, something will need to
% be done about $ signs, which come out as pounds sterling.
\let\ctextfont=\tt \let\ccommentfont=\sl \let\cstringfont=\tt

% Parameters.  Unfortunately \newdimen is \outer (\outerness is a mistake)
% so we need a subterfuge in case we are skipping the file.
\csname newdimen\endcsname\cprogbaselineskip \cprogbaselineskip=\baselineskip
\csname newdimen\endcsname\cprogindent \cprogindent=5pt
\csname newskip\endcsname\beforecprogskip \beforecprogskip=\parskip
\csname newskip\endcsname\aftercprogskip \aftercprogskip=\parskip
\csname newif\endcsname\ifcprogttspace {\let\junk\fi} % if skipping

\def\makeactive#1{\catcode`#1=\active} \def\makeother#1{\catcode`#1=12}
{\obeyspaces\gdef\activespace{ } \obeylines\gdef\activecr{^^M}}
{\catcode`|=\catcode`\\ \makeactive\\ |gdef|activebackslash{\}}
{\catcode9=\active \gdef\activetab{^^I}}
\def\spacewidthof{\fontdimen2}  % Width of a space in the following font.

% The following group makes many characters active, so that their catcodes
% in the \cprogchars macro are active, allowing them to be defined.  We
% could alternatively define more stuff like \activebackslash and use
% \expandafter or (carefully) \edef to expand these in the macro.
\begingroup
\catcode`[=\catcode`{ \catcode`]=\catcode`}
\makeactive! \makeactive" \makeactive' \makeactive* \makeactive- \makeactive/
\makeactive< \makeactive> \makeactive\{ \makeactive\} \makeactive|
\gdef\activestar[*]
\gdef\cprogchars[%
    \makeother##\makeother$\makeother&\makeother\%\makeother^%
    \makeactive"\makeactive'\makeactive*\makeactive-\makeactive/%
    \makeactive<\makeactive>\makeactive{\makeactive}\makeactive|%
    \makeactive!\makeactive\\\makeactive_\expandafter\makeactive\activetab%
    \def!##1[\ifx=##1$\ne$\else\string!##1\fi]%
    \def-##1[\ifx>##1$\rightarrow$\else$\string-$##1\fi]%
    \def"[\cquote"]\def'[\cquote']\def*[$\string*$]%
    % We use \aftergroup in < and > to deal with the fact that #1 might
    % itself examine the following character.
    \def<##1[[$\ifx<##1\ll$\else\ifx=##1\le$\else
      \string<$\aftergroup##1\fi\fi]]%
    \def>##1[[$\ifx>##1\gg$\else\ifx=##1\ge$\else
      \string>$\aftergroup##1\fi\fi]]%
    \def{[\string{]\def}[\string}]\def|[$\string|$]\def~[$\sim$]%
    \expandafter\def\activebackslash[$\backslash$]%
    \let/=\ccomment
    \obeyspaces \expandafter\def\activespace[\leavevmode\space]%
    \expandafter\def\activetab[\ \ \ \ ]%
    \obeylines \expandafter\def\activecr[\strut\par]]
\gdef\cprogarg[\expandafter\def\activebackslash##1[\ifx##1e\let\next\cprogend
    \else$\backslash$\let\next##1\fi\next]\eatcr]
\gdef\cprogend nd#1{cprog#2}[\endcprogarg]      % #1 can be space, #2 *.
\endgroup

\begingroup \makeactive" \makeactive'
\gdef\cquote#1{% #1 is the quote, " or '.
    \begingroup \tt\string#1\cstringfont \makeactive\\%
    \expandafter\let\activebackslash\quotebackslash
    \expandafter\edef\activespace{\ifcprogttspace\char`\ \else\ \fi}%
    \expandafter\let\activecr=\unclosedstring
    \makeother!\makeother*\makeother-\makeother/\makeother<\makeother>%
    \makeother_\makeother\{\makeother\}\makeother|\makeother~%
    \ifx"#1\def'{\char13}\else\makeother"\fi
    \def#1{\tt\string#1\endgroup}}
\endgroup
\def\unclosedstring{%
    \errhelp{A string or character constant earlier in the line was unclosed.^^J
So I'm closing it now.}%
    \errmessage{Unclosed string}%
    \endgroup}
\newlinechar=`^^J
\def\quotebackslash#1{\char`\\%
    \expandafter\ifx\activecr#1\strut\par
      \else\string#1\fi}

% In a comment, we shrink the width of the opening / to that of a space so
% that the stars in multiline comments will line up.  We also shrink the
% closing * for symmetry.
% Note that \end{cprog} is not recognised in strings or comments.
\def\spacebox#1{\leavevmode \hbox to \spacewidthof\font{#1\hss}}
\begingroup \makeactive*
\gdef\ccomment#1{%
    \ifx#1*\begingroup \ccommentfont
      % We want the width of a space in \ccommentfont, not \ctextfont.
      \spacebox{\ctextfont\string/}*%
      \makeother-\makeother'\makeother"\makeother/%
      \expandafter\def\activebackslash{$\backslash$}%
      \makeactive*\let*=\commentstar
    \else \leavevmode\string/#1\kern-1pt %
    \fi}
\makeother* \makeother/
\gdef\commentstar#1{%
    \ifx #1/\endgroup \spacebox{$*$}\string/\let\next\relax%
    \else $*$\let\next#1%
    \fi\next}
\endgroup

% We usually have an active ^^M after \cprog or \begin{cprog}.
\def\eatcr#1{{\expandafter\ifx\activecr#1\else\aftergroup#1\fi}}

% Expand to stretch and shrink (plus and minus) of parameter #1.
\def\stretchshrink#1{\expandafter\eatdimenpart\the#1 \end}
\def\eatdimenpart#1 #2\end{#2}

\ifx\undefined\baselinestretch \def\baselinestretch{1}\fi

\def\cprogsetup{\cprogchars \small \ctextfont \parskip=0pt\stretchshrink\parskip
    \baselineskip=\baselinestretch\cprogbaselineskip \parindent=\cprogindent
    \vskip\beforecprogskip }
\def\endcprog{\endgroup \normalsize \vskip\aftercprogskip}
\def\cprogfile#1{\begingroup \cprogsetup \input#1\endcprog}
% The {cprog} environment or \cprog macro reads in all the argument text.
% By making the C definition of \ much cleverer we could avoid this.
\def\cprog{\begingroup \cprogttspacefalse \cprogsetup \cprogarg}
% Like {verbatim*}, {cprog*} uses `square u' for spaces in quoted strings.
\expandafter\def\csname cprog*\endcsname{%
        \begingroup \cprogttspacetrue \cprogsetup \cprogarg}
\expandafter\let\csname endcprog*\endcsname=\endcprog
% In LaTeX we need to call \end{cprog} properly to close the environment,
% whereas in plain TeX this will end the job.  The test for LaTeX is not
% bulletproof, but most plain TeX documents don't refer to the LaTeX logo.
\ifx\undefined\LaTeX \let\endcprogarg=\endcprog
\else \def\endcprogarg{\ifcprogttspace\end{cprog*}\else\end{cprog}\fi}
\fi

\fi     % \ifx\undefined\cprogsetup

\endinput
